Gas lift valve



Jan. 6, 1942. M. B. THOMAS 3 Sheeis-Sheet l IIII 1 H /////W/////////////I! A 7 7 I! .w ,L 3, q I x I R .-.w x 2 5 1 ,1 w ..m m... 41 u w 8INVENTOR.

ATTORNEY.

3 Sheets-Sheet 2 V///////////////////////f////// B M. B. THOMAS GAS LIFTVALVE Original Filed Feb. l8, 1938 Jan. 6, 1942.

V/////////////////// II H"-7// N l l M. B. THoMAs &As LIFT VALVE m 1 mo3 Sheets-Shet 5 m m J /r//////// /f u 9 a 1 V .Y

Reissued Jan. 6, .1942

Gasur'r VALVE -Manrice B. Thomas, Houston. Tex. i

Original No.

anemi, td October s, 1940," v SerialNo'. sm es-- 13.19::.

Applicatio for reisaue October O, 1841, Serial No.

;s Ciains.

.The present invention is directed` to gas lift valves for use in thepropulsion of liquid from a low level to a higher level. Primariiy. itis concerned with gas-lift valves to be used in oil wells. As is known,a deposit of petroleum oil is usually accompanied by a gas deposit whichpresses down on ,the upper surface of the oil and assists in forcing itto the surface. Inevitably, the oil produced contains more or lesdissolved or suspended gas whereby in -fiowing through tubing from thedeposit to the surface its specific gravity as a liquid is less than theactual specific gravity oi' the gas free oil.

It has been the practice to relyon a decrease of density of oil due toaeration' or gasiiication to increase the flow of oil-in wells in whichthe `rormation pressure has become too low !or normal flow. The aerationhas been accomplished by 'providing valves along the tubing and forcinggas. by one means or another, through` thesevalves into the oil in thetubing thereby imparting a decrease in specific gravity and a liftingaction to thec'oiumn or fluid.

is the provision of a-'valve of the type described which is simple in"construction and has a minimum oi' moving parts. whereby initiai costand maintenance are reduced.

Hitherto, these valves have operated either on the pressure diiferentialprinciple. according to which the head of oil in't-he tubing is directlyopposed to a gas pressur'e outside the tubing, or vice versa, or thevelocity principle, according to which the valve will open when thevelocity of the oil drops below a certain predetermined minimum. Bothtypes have the disadvantage that should the oil in the tubing' orcasing, as the case may be, drop below the level of any of the valves.these valves will open-thereby leading to a waste of gas and an' actualrepression of oilflow. In

addition,when`a string of such val ves is employed. as is usually thecase, more valves than are actually needed are generally set into;operation, thereby causing a'n expensive wasterof gas.

The primary object of* the present invention is the provision'of a valveof-'this general type which operates on a principle quite diiterent fromthom previously relied upon. this principie being thatwhen the flow ofoil in a tubing or casing,

asthecasenaybedecreasesorstopathespeciflc gravity of the liquidincreases due to the less or reduction of gas therein. The' valve of thepresent invention' depends for operation on this h 'change in specificgravity.

A further object of the present invention is the provision or; a valvewhich-so. operates that when a string of them'is eiployed no more thanare actually required will operate to feed gas into the oil.

An additions\ object of the such liquid decreases or steps.

Further objects and advantages of the present invention will appear fromthe following detailed description of the `accompanying drawings. inwhich I Figure i is a side elevation, partly' in section. of a valvearrangement according. to the present invention; v

Figure 2 is a front elevation' of the'arrangement shown inFigure 1;

Figure 3 is a side elevation. partly in section of a modification of thearrangement shown in Fig ra 1: p

Figure 4 is a side elevation. partly in .section. ot anothermodification of the arrangement shown in Figure 1: and

Figure 5 is a side elevation, partly in section. of still anothermodification of the arrangement shown in Pigure 1 I 4 As previouslystated. the valve 'of the present invention depends for-operation uponthe increase in specific gravity of the well liquid due to the' loss o!gas therefrom when-the flow of Buch operation is brought about by thedifference in specific gravity o! the well liquid and a standard liquidhaving a selected specific gravity. In order to provide a uniformterminology in this disclosure and to avoid confusion ofthe various;fluids to which reierence is made. the word fiuicP'as used hereindesignates the pressure fluid or gas which is utilized to propel thewell liquid from alow level to a higher level in the well. The word"liquidY' designates the well liquid although y it is to be understoodthat. as is well known, such member which will correspond in diameter topresent investim ss' the tubing used in the well and which is`providedwith a coupiing 2 on one end and has its other end screwthreaded 'for 'connection in a stringo tubim. This tubim is surroundedin a wellby a casing !I which is o! larger diameter.Thusthevalvemechanisnisarrangedinthenmir space between the tubing andthe using,

" ment is relatively simple.

A casing 3 is attache'd, by welding or otherwise. to the wall of thetubing and is provided with two interier chambers 4 and 5 separated by'adiaphragm 6 in the center oi which is a screw threaded nut 'I in whichis mounted a stud 8 'which terminates as a valve head S adapted to coverport "I, which, when open, connects the space between the casing and thetubing with the interior of the latter through tube I I.

Chamber i is connected to the interier ot tubing l by a short pipe I!which enters tubing I at a point designated as A. Chamber 4 is connectedto the interier of tubing I through a riser il which enters tubing l ata point designate'd as B which may be any selected distance from A andwill usually be at least ten feet above A. The upper end of riser I:actually terminates in the upper end of chamber |4 which is mounted onthe side of the tube. A short length of tubing 'Il connects the lowerend of cha'mber |4 to the interior of tubing I. A plug li is provided inthe upper end of chamber I4 sothat the chamber and the riser and chamber4 may be fllled with the standard liquid. The arrangen'ent oi' riser IIand tubing I! in chamber l4, serves to prevent the standard liquid frombecoming contaminated by the liquid inside tubing l. Riser II isprovided with a choke 11,. to prevent chattering of valve head 9.

The pipe ll connects with the interior oi' tubing i at a point C abovepoint B. The reason !or g this arrangement is that since the gas liftvalve is operated by a diflerence in specific gravity of the liquid intubing I' between point B and' the bottom of the diaphragm 8 and thestandard its operation would become undesirably intermittent ii' the gasadmitted by it were to enter the column of liquid in the tube betweenpoints A and B. In other words, by the arrangement shown'the shuttingoil' oi' the device by its own operation is avoided. Pipe ll isprovided'with a standard check valve II. which may be omitted ifdesired.

The operation of the above described arrangethe riser ll and chamber |4are fllled'with, a standard liquid which has a specific gravityintermediate that of the oil being produced when it is free of gas andwhen it contains enough gas to flow readily under formation pressure,and preferably as close as possible to the latter; that is. the standardliquid in the riser should have a specific gravity approximatng thespecific gravity of the liquid when it is actually flowing. In otherwords, this standard liquid will have a lesser specific gravity thanwould the oil produced after it has been freed from gas.

Let it be 'assumed that oil containing gas is ilowing'into the tubing I.In this case, the colunit Volume than the column of standard liquid v inthe riser, whereupon the pressure in cham'ber i will tend to exceed thatin chamber 4 and push valve head 9 ofl' inlet port lfl, allowing highpressure gas from the casing to pass through pipe il into the tubing Iat point C, thereby liiting the liquid above this point up through thetubing. valve 9 will remain open until by reason liquid in the risertube between the'same points,

The 'chamber 4 and umn oi' liquid in the tubing i between A and B r willbe lighter peruni't Volume than the column ot standard liquid in theriser between the same points. whereby the pressure in chamber 4 will bgreater than that in cham'ber 5 and valve head. 9 will be seated oninlet port II. Any additional head or column of liquid which mayaccumulate in the tubing above the point B will cancel out of theoperation of the device because any pressure thereoflis applied to bothsides of the diaphragm i and may be disregarded. If for some. reason theoil flow in tubing I should of the operation of a lower situated valve,the

weight of the liquid in. tubing I between points A and B again becomesless, or not more, per unit Volume than the weight of the standardliquid in the riser.

The operation of a set, of the-above described valves, installed atgivenintervals in the tubing string of a gas lift well in which liquidfrom the formation rises in both the tubing and the casing, is describedas follows. connected into the oil storaget'anks and the input fluidbeing admitted into the casing, the` liquid level in the-casing will bepushed down until the top valve in the tubing string is uncovered. Ifthe liquid inside the tubing opposite this valve has an equal or greaterspecific *gravity than the standard liquid in the valve riser tube,

the valve will be in the open position and admit' fluid from the casinginto the tubing. unloading any liquid in the tubing above this valve.Liquid will continue to pass through this valve from th casing into thetubing until theliquid level in the casing has been pushed far enoughdown to uncover the next lower valve.

Il' the gas from the formation has escaped from liquid at the elevationof the second valve such liquid will be dead and its specific gravitysufl'cient to have caused that valve tobe in open position and admitfluid from the casing into the inside of the tubing to aerate the deadliquid so that it will rise inside the tubing and lighten the liquidoppodte the valve above sufliciently to close it. Fluid will continue toenter the tubing from the casing through the second valve until theliquid level in the casing has been pushed down far enough touncover'the next lower or third valve and admit gaseous fluid at thispoint.

In like manner, th valves in the tubingstring below this point will beuncovered successively as the liquid level'in the casing is loweredbythe gaseous fluid iniected into the casing, closing the next highervalve as the valve underneath ad- 'mits gaseous fluid into the tubingstring, until a point will be reached `where the available input fluidpressure -on the casing will push the liquid level in the casing down nofarther, 'at which point gaseous fluid will continue to pass from thecasing into the tubing through the lowest* valve above the liquid levelin the casing that has a greater pressure outside the tubing thaninside, all vaives above this 'valve remaining closed.

Should the casing pressure 'at' the surface 'decreas sufliciently topermit the liquid level in the casing to rise above the valve whereg'aseous fluid is being admitted into the tubing. then the admission ofgaseous fluid into the tubing will be cut ofl' and flow up the tubingstring might then stop for want of gas to sufllciently aerate' liquid inthe tubing and permit dead liquid to settle back down the inside oi' thetubing. When this dead liquid inside the tubing rises to the -flrstvalve above the'liquid level in thecasing,

, the specific gravity of the liquid in the tubing stop. the specificgravity of the liquid between points A and B will gradually increase dueto gas less until this column becomes heavier per u will .then be greatenough to open this valve and admit gas from the casing into the tubingand resume flow out ot the well. The valves will With the well tubing ofto its interior.

and to the wall ol' tubingiand plug IS is 'riser.

4 I 21,998 reactin'a similar manner to slugs of liquid being and thecasing and high pressure gas is fed in through the tubing. For thisreason, pipes z and li open to the exterior of tubing I instead This isalso true of tube ll. Inlet port II, on the other hand, is connected' tothe interior oi tubing I by an addltional tube s. w

The arrangement shown in Figure 4 diifers from that shown in Figura' 1only in that the valve assembly is aflixed to the interior of the tubingI instead of to its exterior. `'I'o this end the plug which carries theinlet port ll is extended through the wall of tubing l so as tocommunicate with the space between the tubing' the liquid being producedfrom the deposit ini creases with depth. consequently, the deeper'in thewell the valve is placed, the closer will the liquid in the conduitapproach the dead oil in the riser in specific gravity and the greaterwill the tendency or the valve to remain open become.

. height ot the riser and/or increasing the size of and the casing.Like'wise, since plug IC must be 2 accessible outside'the tubing, a pipe2! is connected to the opening at the top of chamber ll inserted intothe end of this pipe. A r

The arrangement shown in Figure 5 is used for weils in which the flow ofoil is upwardly between the tubing and the casing. In order to providefor this, tube ll is extended to the wall of the tube i andcommunicates' with the exterior thereof. Likewise,-pipes I! and II,instead of terminating inside o! tubing I, are extended to the wall oitubing I and communicate with the exterior thereof. otherwise thearrangement is precisely the same as that illustrated in Figure 4,except that the port, ll communicates with the inside of the tubing l'instead of 'the outside.

The above discussion has been based on an assembly in which the valve iis on itsseat when the diaphragm is in neutralposition and the standardliquid in the riser has a specific gravity less than that of the oilproduced from the well when it is free oi gas. It is apparent that thecombination of parts will function similarly when valve 9 is of suchlength as to be oi! its seat when the diaphragm is in neutral positionand a standard liquid having the same gravity as the oi-l produced whenit is free of gas is employed in the riser. In many cases thisarrangement will be more convenient since it permits the use oi dead oilproduced from the deposit in the riser; With this oil in the riser thelength of the valve and the strength of the diaphragm 0 .1 be soadjusted that the valve will remain open until the liquid in the conduitbeing produced from the deposit has a gravity which may, for example, beat least less than the specific gravity of the dead oil consequently,when the oil in the conduit contains 'enough gas to ;flowjthe valve willbe closed by reason of the greater specific gravity oi the dead oil inthe As flow inithe conduit diminishes and the specific gravity of theliquid in the conduit inicreases' by reason of loss of gas, andapproaches the specific gravity of the dead oil in the riser, the valvewill open and start the injectionof gas into the conduit.

This latter'arrangement hasthe distinct advantage that it helps makepossible the maintenance of the lowest exposed valve on the string of'tubing in open position. The specific gravity ot various changes in theabove described arrangements may occur to those skilled in'the art. Forexample, the sensitivity of the valve assembly may be incre'ased byincreasing the the diaphragm. Positive action oiithe valve may be aidedby the arrangement of suitably selected spring: on either or both sideso! the diaphragm or around the valve stem. The particular type of valveillustrated, which was designedly chosen simply for ease of description,may be replaced by any one of the number of known valves of diflerentdesign.

All such changes in arrangement of parts and u size and design ofindividual elements which do not involve a departure from the basicprinciples underlying the present invention are contemplated within 'thescope of the appended claims in which it is intended to claim theinvention as broadly as the prior art permits.

What is claimed is:

l. An assembly for the production of liquid from' a subsurfacedepositcomprising a conduit establishing liquid connection between saiddeposit and the surface, a source of high pressure gas, a passageconnecting said source to the interior of said conduit, a valve forcontrolling said passage, and means sensitive to the specific gravity o!the liquid in said conduit solely at a point below the point of;connection thereto oi said gas passage `for flxing the position ofsaidvalve. 3

2, An assembly for the productioof oil from a subsurface depositcomprising a conduit establishing liquid connection between said depositand the surface, a diaphragm arranged adjacent the wall of said conduit,a source of high pres-- sure gas, a passage connecting said source tothe interior of said conduit, a valve` for controlling said passageactuated by said diaphragm, a

chamber on 'each side of said diaphragm, means connecting oneof saidchambers to the interior of said conduit, means for maintaining-aconstant head of standard liquid oi! selected specific gravity connected'to the other chamber and means connecting the top of said head ofstandard liquid to the interior of said conduit.

3. In an assembly for producing oil from a sub-surface formation, incombination, a conduit for leading the oil from the formation to thesurface. a source of high pressure gas normally maintained` out oi'fluid connection with said conduit by a valve, means adjacent the wallof said conduit for holding a column of liquid ot selected specificgravity, means for opposing 4. In an assembly for p'roducing oil rrom asubsurface formation, in combination, a conduit i for leading the oil!rom the rormation to the surface, a source of high pressure gasnormally i maintained out of fluid connection with said conduit by avalve, means adjacent the wall of said `conduit for holding a column oiliquid of selected specific gravity. means for opposing said column to acolumno liquid oi the same height in the conduit, and means actuated bya difl'erence in specific gravity between the liquids of said columns infavor of the liquid of selected specific gravity for opening theatoresaid valve.

5. A flow valve of the character described having its component partsmounted adjacent the said fluid outlet 'passag to the interior of saidconduit and a valve for controlling said inlet passage having its sternpassing' through said partition andattached to said diaphragm andmeans-for actuating said diaphragm.

6. In an assembly tor producing oii from a sub-surface formation, incombinat'ion, a conduli; for leading the oil from the i'ormation to thesurface, .a source of high pressure gas, a pair of juxtaposei chambersseparated by a partition arranged 'adjacent a wall oi' said conduit,

-a diaphragm in one of said chambers dividing it into two sections, atube connecting one oi' said sections to the interiorof the conduitat agiven point, a riser adapted to hold a liquid of selected specificgravity extending upwardly from the other section, said riserbeingafluidiy connected to the interior of said conduit at a' pointabove the aioresaid given point, a fluid connection between the secondchamber and the interior of said conduit at a point above the point ofconnection of the riser thereto, a fluid sponse to variationsdn thespecific gravity of the oil in a relative y short section in'saidconduit.

10. A gas lift apparatus for oil wells comprising a conduit for carryingoil from the producing formation to the surface, means' for introducinggas under pressure at a selected point in said conduit, and meansresponsive to variations in the speciflc gravity of oil in said conduitsoiely at a point below said point of introduction of gas Ior-regulatingthe flow of gas into the conduitu 11. Apparatus for maintaining aconstant gas oil ratio in a liquid eduction pipe in a gas lift wellincluding means for opposing a head of liquid of selected specificgravity against a corresponding head of oil in said pipe. means forsupplying gas into the induction pipe, and means for varying the supplyof gas into said pipe in proportion to variations in specific gravity insaid selected head of oil in said pipe.

12. A gas lift device for producing liquid from an earth borecomprising, a tubular member through which th'e production iiquid flows,said member having a passage for admitting gas under pressure into themember through the wall thereoi', and means for opening and closing saidpassage soleiy in response to variaticns in the specific gravity of theliquid extending along a relatively short section of the member.

13. A gas lii't device, for producing iquid from an earth bore.com`prising. a -tubular member adapted to be lowered into the earthbore and fluid connection with the interior oi' the conduit.

8. In an assembly tor producing oil from a subsurface tormation, inccmbination, a conduit tor leading the oil from the tormation to thesurface, a source of high pressure gas, a passage connecting said sourceto the interior of .said conduit at a selected point, a valve !orcontrolling said passage, means adjacent the wall o! said conduit forholding ,a column of liquid of selected specific gravity, means tor osaid column to a column oi' liquid of selected height in said conduit,said latter column being below the point oi' connection oi', said highpressure gas passage to said conduit. and means actuated by changes inspecific gravity in said column oi' conduit liquid for controiling theposition oi' the aforesaid valve.,

9. An assembly for producing oil from a subsurface iormation comprisinga'conduit i'cr carrying' oil from the !ormation to the surface, meansfor introducing gas under pressure at a point in said conduit, and meanstor reguiating the flow oi' gas into the conduit soiely in reconductwell liquid upwardiy therein, said member having a passage in the wallfor the admission of gas under pressure through `the passage and intothe member, and means for opening and closing said passage, said meansbeing responsive to a predetermined specific gravity ot the liquid alonga relatively short section oi' the member to open said passage andthereai'ter responsive to a predetermined lesser specific gravity of theiiquidalong the relativeiy short section to close the passage.

14. A gas lift device for producing liquid comprising a tubular memberhaving a passage in the wall thereof for the admission of a gas underpressure i'rom the exterior 'to the interior thereoi', and means foropening and closing said passage, said means being responsive topredetermined difl'erent higher and-lower specific gravitles ot theliquid' solely along a relatively short section of the member torespectiveiy' open and close the passage. 2

15. A gas lift apparatus for o'il wells comprising a tubular member, aconduit to which said tubular member is adapted forconnection !or carying iiquid` from the producing formation to the surface, means torintroducing gas under pressure at a selective point in said member, and

means responsive to variations in the specific gravity of liquid in saidmember solely at a point below-said point of introduction ofgas i'oradmitting the flow oi' gas into the member.

- MAU'RICE B THOMAS.

